(a) Field
The present invention generally relates to a discovery method and apparatus in a device-to-device direction communication.
(b) Description of the Related Art
Recently, interest in a device-to-device (D2D) direct communication is increasing for providing a proximity-based service. Accordingly, various techniques for supporting the D2D direct communication are developed.
The procedures of the direct communication may be classified into a discovery procedure identifying and discovering neighbor devices for the D2D direct communication and a procedure establishing a communication path with the neighbor devices and performing the direct communication through the established path.
In the discovery procedure, device identifier information and service-related information provided by the device may be obtained. For the discovery, a device joining in the D2D direct communication may periodically provide own device identifier information or service information to neighbor devices in a broadcasting manner. Alternatively, the device may obtain identifier information and target service information of the neighbor device in a query-based manner exchanging a request/response message with the neighbor device.
Since few radio resources are required for broadcasting the identifier information of the device, overhead due to the periodic broadcast is not relatively high. However, if the device providing many services periodically broadcasts all information for the services, the overhead is increased and the efficiency of radio resources is decreased. Accordingly, in the conventional arts, the device does not broadcast the service information through a radio channel. The neighbor device establishes a communication path with the device and receives the service information from the device through the established path. However, the neighbor device should always negotiate with the device for the service after establishing the communication path with the device even if the device does not provide the service. Therefore, unnecessary communication path can be established between the neighbor devices.
In case of the query-based manner exchanging the request/response message, the small amount of information can be included in the request/response message since only necessary service information is provided. Further, the query-based manner can provide the device with the response message faster than the broadcasting manner. However, the efficiency of resources may be deteriorated since resources used in the neighbor devices can be collided when the request message and the response message are transmitted. Furthermore, in the broadcasting manner, the device can know status change of the neighbor devices through the periodically broadcasted information. However, in the query-based manner, the device can know the status change of the neighbor devices only with exchanging messages.